Chemicals may be stored in one location and used for processing at the same or different locations. Many facilities have emergency shower systems and/or eyewash units (“SS/EWs”) near where the chemicals are stored, used or otherwise handled. The SS/EW allows an individual contaminated with chemicals to easily direct a spray of water at himself or herself to wash off the chemicals. Some SS/EWs provide a downward-facing shower head and a pulling lever that will start the flow of water out of the shower head to wash the chemicals off the contaminated person. SS/EWs can also have an upward-facing spray nozzle head and a paddle to start an upward flow of water, thereby washing the chemicals off the person's face and/or eyes. The SS/EW may also be actuated by a rescuer or other person to wash chemicals off a contaminated individual.
Water is frequently used in an SS/EW because water itself often will not act as a catalyst to speed up the reaction of the chemical with the individual's skin. It is highly desirable to provide water from the SS/EW within an ideal temperature range of 60 to 90 degrees Fahrenheit.
Dual faucet arrangements could be used to control the temperature of the water, but such arrangements may be difficult for a person to operate in a state of panic, pain or both. Thus, many conventional water supply systems for SS/EWs do not use such an arrangement. Instead, water supplies to SS/EWs may use a thermostatic mixing valve coupled to both a cold water supply and a hot water supply from a hot water heater to automatically control the temperature of the water dispensed from the SS/EW. A thermostatic mixing valve is supposed to mix the water from the two sources to achieve a preset temperature.
However, thermostatic mixing valves and the systems containing them are not well suited to water supply systems for SS/EWs for several reasons. One problem with thermostatic mixing valves is their period of thermal stabilization. There is a stabilization period when the water first starts flowing through a thermostatic mixing valve. During the stabilization period, the water may have a temperature that is outside the ideal temperature range. The stabilization period of a thermostatic mixing valve increases the longer the valve is not in use. Because SS/EWs may be rarely used, the stabilization period may become unacceptably long.
Another problem with thermostatic mixing valves is the amount of pressure required behind the valve for proper operation. If the pressure decreases behind the valve due to other demands of the source of hot or cold water simultaneous to use of the SS/EW, the thermostatic mixing valve may not operate properly.
Another problem with thermostatic mixing valves is their capacity. The valves operate properly only within a specified flow range that may not be able to supply adequate flow at the specified temperature for simultaneous operation of multiple SS/EWs. Multiple SS/EWs may be hooked to a single supply to supply several areas with multiple showers at a reasonable cost. In many circumstances, only one shower is operated at a time, well within the stable range of the thermostatic mixing valve. However, should the simultaneous operation of multiple showers be necessary, for example, in an accident where many people come into contact with chemicals or where a rescuer comes into contact with chemicals while placing an individual into one shower and needs to use a nearby shower, the valve may not be able to supply the multiple showers within the ideal temperature range.
One problem with systems using thermostatic mixing valves is that they may need to be custom built on-site by plumbers during construction of the facility in which the SS/EW is being installed. Custom building such systems is undesirable for several reasons. First, it is more expensive than premanufactured systems due to tradesmen's salaries and design costs. Second, it is difficult to achieve the level of quality in custom built systems possible in premanufactured systems because, the people building such systems may not have the experience building such systems that would be possible by a person in a factory. Further, a premanufactured system may be factory tested and inspected by a quality control engineer before it is shipped to the facility where it will be installed. Such testing may be more thorough than what might be expected of a tradesman in the field.
Another problem with systems using a thermostatic mixing valve is the delay before the temperature controlled water reaches the shower head of the SS/EW. Because the ambient temperature of the pipes between the thermostatic mixing valve and a shower head may be different than the ideal temperature of the water supplied by the thermostatic mixing valve, the water in the pipes between the valve and the shower head may be at a temperature outside the ideal temperature range. This is a particular problem for showers located outside the facility in which the valve is located, because the pipes leading to the shower head may be subjected to temperatures other than room temperature.
Some systems wrap the pipes subject to ambient temperatures below the ideal temperature range in heat trace, which can warm the pipes if the temperature ambient to the pipes becomes too cold. However, the failure of the heat trace can leave the water too cold, and if the thermostat controlling the temperature of the heat trace fails, the water in the pipes surrounded by the heat trace may get too cold or too hot.
Another problem with systems using a thermostatic mixing valve is the relative inefficiency of the water heater used to heat the water as compared with other sources of heat that may be available, such as hot water or steam from a central plant in the facility which the SS/EW system serves. The water in the heater is typically heated to 140 degrees Fahrenheit while sitting in an ambient temperature at or near room temperature. The water in the water heater loses heat to its environment, requiring additional energy to be expended to maintain its temperature at or near 140 degrees Fahrenheit.